U.S. patent application number 11/051941 was filed with the patent office on 2006-08-10 for imprint lithography template to facilitate control of liquid movement.
This patent application is currently assigned to Molecular Imprints, Inc.. Invention is credited to Pankaj B. Lad, Ian M. McMackin, Van N. Truskett.
Application Number | 20060177535 11/051941 |
Document ID | / |
Family ID | 36780249 |
Filed Date | 2006-08-10 |
United States Patent
Application |
20060177535 |
Kind Code |
A1 |
McMackin; Ian M. ; et
al. |
August 10, 2006 |
Imprint lithography template to facilitate control of liquid
movement
Abstract
The present invention is directed to a template that features a
control surface extending from a periphery of a mold toward a
recessed surface of the template forming an oblique angle between a
portion of the control surface disposed proximate to the
periphery.
Inventors: |
McMackin; Ian M.; (Austin,
TX) ; Lad; Pankaj B.; (Austin, TX) ; Truskett;
Van N.; (Austin, TX) |
Correspondence
Address: |
MOLECULAR IMPRINTS
PO BOX 81536
AUSTIN
TX
78708-1536
US
|
Assignee: |
Molecular Imprints, Inc.
|
Family ID: |
36780249 |
Appl. No.: |
11/051941 |
Filed: |
February 4, 2005 |
Current U.S.
Class: |
425/385 |
Current CPC
Class: |
B82Y 10/00 20130101;
G03F 7/0002 20130101; B82Y 40/00 20130101 |
Class at
Publication: |
425/385 |
International
Class: |
B29C 59/00 20060101
B29C059/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] The United States government has a paid-up license in this
invention and the right in limited circumstance to require the
patent owner to license others on reasonable terms as provided by
the terms of 70NANB4H3012 awarded by National Institute of
Standards (NIST) ATP Award.
Claims
1. A template comprising: a mold having a periphery lying in a
plane; a recessed surface spaced-apart from said plane; and a
control surface extending from said periphery toward said recessed
surface, with an oblique angle being defined between a portion of
said control surface disposed proximate to said periphery and said
plane.
2. The template as recited in claim 1 further including a sidewall
with said control surface extending between said sidewall and said
periphery and said sidewall extending between said control surface
and said recessed surface.
3. The template as recited in claim 1 wherein said control surface
substantially surrounds said mold.
4. The template as recited in claim 1 wherein said control surface
terminates at said recessed surface.
5. The template as recited in claim 1 wherein said control surface
has an arcuate shape.
6. The template as recited in claim 1 wherein said control surface
has a linear shape.
7. The template as recited in claim 1 wherein said control surface
has a concave shape.
8. The template as recited in claim 1 wherein said control surface
has a convex shape.
9. The template as recited in claim 1 further comprising a mesa
wall surface positioned between said recessed surface and said
control surface, with said sidewall surface extending orthogonally
to said recessed surface.
10. The template as recited in claim 1 further wherein said mold
has a surface energy associated therewith that is greater than a
surface energy of said control surface.
11. A template comprising: a mold having a periphery lying in a
plane; a recessed surface spaced-apart from said plane; a sidewall
surface; and a control surface extending between said periphery and
said sidewall surface, with an oblique angle being defined between
a portion of said control surface disposed proximate to said
periphery and said plane, said sidewall surface extending between
said control surface and said recessed surface, with said recessed
surface extending orthogonally to said sidewall surface.
12. The template as recited in claim 10 wherein said control
surface substantially surrounds said mold.
13. The template as recited in claim 10 wherein said control
surface terminates at said recessed surface.
14. The template as recited in claim 10 wherein said control
surface has an arcuate shape.
15. The template as recited in claim 10 wherein said control
surface has a linear shape.
16. The template as recited in claim 10 wherein said control
surface has a concave shape.
17. The template as recited in claim 10 wherein said control
surface has a convex shape.
18. A template comprising: a mold having a periphery lying in a
plane; a recessed surface spaced-apart from said plane; and a
control surface extending from said periphery toward said recessed
surface, with an oblique angle being defined between a portion of
said control surface disposed proximate to said periphery and said
plane, with said mold has a surface energy associated therewith
that is greater than a surface energy of said control surface.
19. The template as recited in claim 18 wherein said control
surface has a shape associated therewith selected from a set of
shapes consisting essentially of a linear shape, a concave shape
and a convex shape.
20. The template as recited in claim 18 further including a
sidewall with said control surface extending between said sidewall
and said periphery and said sidewall extending between said control
surface and said recessed surface, with said sidewall and said
recessed surfaces each having a surface energy associated therewith
that is less than a surface energy of said mold.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a divisional application of U.S.
patent application Ser. No. 11/051,533 entitled "Imprint
Lithography Template to Control Extrusion of a Liquid from a
Desired Region on a Substrate," naming inventors Edward B.
Fletcher, Ian M. McMackin, Michael N. Miller, Nicholas A. Stacey,
Wesley Martin, Frank Y. Xu, Christopher J. Mackay and Van N.
Truskett, filed Feb. 4, 2005, which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0003] The field of the invention relates generally to
micro-fabrication techniques. More particularly, the present
invention is directed to a template to control movement of a liquid
suitable for imprint lithography.
[0004] The prior art is replete with examples of exemplary
micro-fabrication techniques. One particularly well-known
micro-fabrication technique is imprint lithography. Imprint
lithography is described in detail in numerous publications, such
as United States published patent application 2004/0065976 filed as
U.S. patent application Ser. No. 10/264,960, entitled "Method and a
Mold to Arrange Features on a Substrate to Replicate Features
having Minimal Dimensional Variability"; United States published
patent application 2004/0065252 filed as U.S. patent application
Ser. No. 10/264,926, entitled "Method of Forming a Layer on a
Substrate to Facilitate Fabrication of Metrology Standards"; and
United States published patent application 2004/0046271 filed as
U.S. patent application Ser. No. 10/235,314, entitled "Method and a
Mold to Arrange Features on a Substrate to Replicate Features
having Minimal Dimensions Variability"; all of which are assigned
to the assignee of the present invention. The fundamental imprint
lithography technique as shown in each of the aforementioned
published patent applications includes formation of a relief
pattern in a polymerizable layer and transferring a pattern
corresponding to the relief pattern into an underlying substrate.
To that end, a template, having a mold, is employed. The mold is
spaced-apart from, and in superimposition with, the substrate with
a formable liquid present therebetween. The liquid is patterned and
solidified to form a solidified layer that has a pattern recorded
therein that is conforming to a shape of a mold. The substrate and
the solidified layer may then be subjected to processes to
transfer, into the substrate, a relief image that corresponds to
the pattern in the solidified layer.
[0005] One manner in which to locate the polymerizable liquid
between the template and the substrate is by depositing the liquid
on the substrate as one or more droplets, referred to as a drop
dispense technique. Thereafter, the polymerizable liquid is
concurrently contacted by both the template and the substrate to
spread the polymerizable liquid over the surface of the substrate.
It is desirable to have the liquid confined to an area of the
substrate in superimposition with the mold.
[0006] Thus, there is a need to provide greater control over
movement of a liquid during imprint lithographic processes.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a template that
features a control surface extending from a periphery of a mold
toward a recessed surface of the template forming an oblique angle
between a portion of the control surface disposed proximate to the
periphery. In this fashion, a capillary force gradient may be
created between imprinting material and the surface of the template
facing the imprinting material. This provides greater control over
a quantity of imprinting material extruding from a volumetric gap
defined between the mold and a region of a substrate in
superimposition. As a result, formation of undesirable artifacts
during imprint lithography is reduced, if not avoided. These and
other embodiments of the present invention are discussed more fully
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a cross-sectional view of a template, having
disposed opposite to a substrate with imprinting material disposed
therebetween, in accordance with the prior art;
[0009] FIG. 2 is a cross-sectional view of a solidified imprinting
layer formed upon the substrate employing the template shown in
FIG. 1, having a conformal layer disposed thereon in accordance
with the prior art;
[0010] FIG. 3 is a simplified top-down view of the conformal layer
shown in FIG. 2, in accordance with the prior art;
[0011] FIG. 4 is a cross-sectional view of a template, having
disposed opposite to a substrate with imprinting material disposed
therebetween, in accordance with the present invention;
[0012] FIG. 5 is a cross-sectional view of a template shown in FIG.
4 in accordance with a first alternate embodiment of the present
invention;
[0013] FIG. 6 is a cross-sectional view of a template shown in FIG.
4 in accordance with a second alternate embodiment of the present
invention;
[0014] FIG. 7 is a cross-sectional view of a template shown in FIG.
4 in accordance with a fifth alternate embodiment of the present
invention;
[0015] FIG. 8 is a cross-sectional view of a template shown in FIG.
4 in accordance with a sixth alternate embodiment of the present
invention; and
[0016] FIG. 9 is a cross-sectional view of a template shown in FIG.
4 in accordance with a seventh alternate embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring to FIG. 1, a template 10 is shown in contact with
imprinting material 12, with imprinting material 12 being disposed
between a mold 14 and substrate 16 in furtherance of patterning
imprinting material. To that end, mold 14 is spaced-apart from
substrate 16 and imprinting material 12 substantially fills a
volumetric gap defined between mold 14 and a region 18 of substrate
16 in superimposition therewith. Thereafter, imprinting material 12
is solidified by exposing the same to an actinic component. In this
manner, the shape of a surface 20 of mold 14, facing imprinting
material 12, is recorded therein by formation of solidified
imprinting layer 22, shown in FIG. 2.
[0018] Referring to FIGS. 1 and 2, surface 20 of mold 14 is
patterned by inclusion of a plurality of protrusions 24 and
recessions 26. The apex portion of each of protrusions 24 lies in a
common plane, P. It should be understood, however, that surface 20
may be substantially smooth, without protrusions 24 and recessions
26, if not planar.
[0019] The actinic component employed to solidify imprinting
material 12 may be any known substance, depending upon the
composition of imprinting material 12. Exemplary compositions for
imprinting material 12 are disclosed in U.S. patent application
Ser. No. 10/763,885, filed Jan. 24, 2003, entitled "Materials and
Methods for Imprint Lithography," which is incorporated by
reference. As a result, the actinic component employed is typically
ultraviolet wavelengths, and mold 14, not the entire template 10,
is fabricated from fused silica. However, other actinic components
may be employed, e.g., thermal, electromagnetic and the like.
[0020] Imprinting material 12 may be deposited upon either
substrate 16 and/or template 10 employing virtually any known
technique, dependent upon the composition employed. Such deposition
techniques include but are not limited to, chemical vapor
deposition (CVD), physical vapor deposition (PVD) spin-coating, and
drop dispense techniques. After formation of solidified imprinting
layer 22, mold 14 is separated therefrom, and solidified imprinting
layer 22 remains on substrate 16. Solidified imprinting layer 22
includes residual regions 28 having a thickness t.sub.1 and
projections 30 having a thickness t.sub.2, with t.sub.1 being 10 nm
or greater and t.sub.2 being 40 nm or greater. Control of the
dimensions of features recorded in solidified imprinting layer 22
is dependent, in part, upon the volume of imprinting material 12 in
superimposition with region 18. As a result, attempts have been
undertaken to confine imprinting material 12 to the volumetric gap
during imprinting processes.
[0021] One attempt to confine imprinting material 12 to the
volumetric gap includes forming mold 14 on template 10 as a mesa.
To that end, mold 14 extends from a recessed surface 21 of template
10 and terminates in plane. Sidewall 23 functions to assist
confining imprinting material 12 within the volumetric gap due to
the lack of capillary attraction between imprinting material 12 and
mold 14 outside the volumetric gap. Specifically, sidewall 23 is
provided with sufficient length to reduce the probability that
capillary attraction between recessed surface 21 and imprinting
material 12 occurs.
[0022] Occasionally during the imprinting process, imprinting
material 12 may extrude beyond the volumetric gap so as to lie
outside of region 18 and/or surface 60. This may be due to, inter
alia, fluid pressure generated in imprinting material 12 while
being compressed between substrate 16 and mold 14. Further, the
fluid pressure causes a sufficient quantity of imprinting material
12 to extrude beyond the volumetric gap so that capillary
attraction between this material and recessed surface 21 occurs. As
a result, formed, proximate to the periphery of region 18, are
extrusions 32. Extrusions 32 have a thickness t.sub.3 that may be
several orders of magnitude larger than thicknesses t.sub.1 and
t.sub.2, depending upon the spacing between surface 34 and region
18. For example, thickness t.sub.3 may be 2 .mu.m-15 .mu.m. The
presence of extrusions 32 may be problematic. For example,
imprinting material 12 contained in extrusions 32 may not
completely cure when exposed to the actinic component. This may
result in imprinting material 12 accumulating at a periphery 36 of
mold 14. Additionally, upon separation of mold 14 from solidified
imprinting layer 22, imprinting material 12 in extrusions 32 may
spread over the remaining portions of substrate 16 lying outside of
the volumetric gap. Additionally, extrusions 32 may become cured,
which can result in same remaining on substrate 16 as part of
solidified imprinting layer 22. Any of the aforementioned effects
of extrusions 32 can generate unwanted artifacts during subsequent
imprinting processes.
[0023] Referring to FIGS. 2 and 3, were extrusion 32 partially
cured, for example, control of the thickness of subsequently
disposed layers becomes problematic. This is shown by formation of
multi-layered structure 38 resulting from the deposition of a
conformal layer 40 upon solidified imprinting layer 22. In the
present example, conformal layer 40 is formed employing spin-on
techniques as discussed in U.S. patent application Ser. No.
10/789,319, filed on Feb. 27, 2004 entitled "Composition for an
Etching Mask Comprising a Silicon-Containing Material." The
presence of extrusions 32, however, reduces the planarity of the
surface 42 ordinarily expected from spin-on deposition of conformal
layer 40. The presence of extrusions 32 results in the formation of
deleterious artifacts, such as thickness variations, in conformal
layer 40. These deleterious artifacts present as protrusions in
surface 42, are generally referred to as comets 44. Comets 44 are,
typically, undesirable artifacts, because the same produce peaks 46
and troughs 48 in surface 42. As a result, surface 42 is provided
with a roughness that hinders patterning very small features.
Similar roughness problems in subsequently formed surfaces arise in
the presence of artifacts generated by extrusions 32.
[0024] Referring to FIG. 4, to avoid the deleterious artifacts, the
present invention reduces, if not prevents, an amount of imprinting
material 12 from extruding outside the volumetric gap. To that end,
a template 50 includes a mold 52 layer and both are substantially
the same as discussed above with respect to template 10 and mold
14, excepting that template 50 includes a capillary force control
(CFC) surface 54. CFC surface 54 extends between mold 52 and
sidewall 56 forming an angle .PHI. with respect to plane P. CFC
surface 54 functions to control, if not prevent, a quantity of
imprinting material 12 from extruding outside the volumetric gap by
avoiding an orthogonal angle being formed between periphery 53 of
mold 52 and CFC surface 54. Specifically, it was recognized that a
certain quantity of imprinting material 12 may extend beyond the
volumetric gap defined between region 18 and surface 60 in
superimposition therewith. With this realization, implemented is
control, rather than avoidance, of imprinting material extruding
from the volumetric gap. To that end, CFC surface 54 is selected to
produce a gradient of capillary forces proximate to periphery 53,
with imprinting material 12 that comes in contact therewith. This
is achieved, in part, by forming an oblique angle .PHI. between CFC
surface 54 and periphery 53.
[0025] CFC surface 54 extends upwardly away from plane P and
outwardly away from region 18, producing a linear increase in the
distance with respect to substrate 16 to a maximum distance d and
without having to vary the volumetric gap, i.e., the volume of the
volumetric gap remains constant. The result of the linear increase
in the distance of separation between template 50 and substrate 16
produces a force gradient in the capillary forces generated by
contact between imprinting material 12 and CFC surface 54.
Specifically, the farther imprinting material 12 extrudes from the
volumetric gap, the greater the distance d between CFC surface 54
and substrate 16; hence, the lesser the capillary forces. By
selecting the appropriate angle .PHI. and length of CFC surface 54,
the amount of a given imprinting material 12, subjected to a given
compression force between surface 60 and region 18, extruding
beyond the volumetric gap may be controlled. This, in turn,
facilitates control over the size of extrusions and/or the quantity
of uncured imprinting material 12 that may spread to other regions
of substrate 16 during separation of mold 52, after solidification
of imprinting material 12 as discussed above. It is desired,
however that the aspect ratio of width and height of CFC surface
54, as defined by the length and angle .PHI. be on the order of the
protrusions and projections.
[0026] It should be understood that gradually decreasing capillary
forces between imprinting material 12 and template 50 may be
achieved by providing CFC surface 54 with a variety of shapes. For
example, CFC surface 54 may be configured so that the distance
between the surfaces of template 50 and substrate 16 vary
exponentially, while maintaining a constant volumetric gap. To that
end, CFC surface 54 may have a concave shape shown as surface 154,
in FIG. 5, or a convex shape, shown as surface 254 in FIG. 6, with
the angle .PHI. formed between periphery 53 and one of surfaces 154
and 254 being an oblique angle. The rate of curvature of surfaces
154 and 254 are established such that the quantity of imprinting
material 12 extending beyond region 18 remains within desired
parameters.
[0027] In a further embodiment, capillary force control (CFC)
surface 554 extends between plane P and recessed surface 547, shown
in FIG. 7, i.e., without the presence of sidewall 23 as shown in
FIG. 4. To that end, CFC surface 654 may extend between plane P and
recessed surface 657 so as to have a concave shape, shown in FIG. 8
or a convex shape, shown as surface 757 extending between plane P
and recessed surface 747 in FIG. 9.
[0028] Referring again to FIG. 1, in a further embodiment, to
further improve the control of extrusion of imprinting material 12
beyond region 18, the wetting characteristics of CFC surface 54,
and/or mesa sidewalls 23 and/or recessed surface 21 may be reduced,
or minimized, when compared to the wetting characteristics of
surface 20. In this manner, the surfaces of template 10 facing
substrate 16 are provided with differing wetting characteristics.
One manner in which to achieve this is to establish the appropriate
surface energies, for a given imprinting material 12, among the
various surfaces of template 10. For example, it is desired to
establish surface 20 to have the lowest surface energy
characteristics.
[0029] Referring to FIG. 4, implementing these principles in
conjunction with template 50 may facilitate greater control over
the extrusion of imprinting material 12 outside of the volumetric
gap. For example, the desired surface energy for surface 54, or
mesa sidewall 55 and recessed surface 57, may be established based
upon the surface tension of imprinting material 12 and the surface
energy of patterned surface 60 of mold 52. It should be understood
that it is not necessary that each of CFC surface 54, mesa sidewall
55 and recessed surface 57 have the same surface energy.
[0030] One manner in which to establish the surface energy of CFC
surface 54, mesa sidewall 55 and recessed surface 57 employs
application of a low surface energy coating formed by methods
including, but not limited to, chemical vapor deposition (CVD),
physical vapor deposition (PVD), thermal oxidation, and ion
implantation. An exemplary technique, to that end, may include
application of fluorine-containing materials, such as electroless
nickel coating containing fluorinated particles.
[0031] Moreover, a fluorinated composition employed for the low
surface energy coating may be dissolved or dispersed in a solvent
or other suitable fluid which may be applied to the desired
surfaces of template 50 employing one or more of a plurality of
methods: dipping, spraying, and brushing. Additional processing may
improve the density of the low surface energy coating and increase
the bonding of the low surface energy coating to improve the
durability of the same. Alternatively, a fluorine-containing
compound may be left upon the desired surfaces of template 50 by
exposing the same to fluorine-containing etchant chemistries.
[0032] An exemplary fluorine-containing composition includes a
solution comprised of a hydrofluoroether solvent and
tridecafluoro-1,1,2,2,-tetrahydrooctyltrichlorosilane (FOTS). The
solution may be dispensed via a pipette upon one or more of CFC
surface 54, mesa sidewall 55 and recessed surface 57. The ratio of
FOTS to hydrofluoroether is approximately 1 microliter of FOTS per
3.5 milliliters of hydrofluoroether. The component hydrofluoroether
is available from 3M located in St. Paul, Minn. under the trade
name HFE-7100DL. After application of FOTS, the template may be
dried employing nitrogen. Another fluorine-containing composition
may include a solution of a mono-functional silane having a
perfluoropolyether backbone or a di-functional silane having a
perfluoropolyether backbone in a fluorinated solvent.
[0033] Other materials and processes may be employed to vary
surface energies of various surfaces of template 50. For example, a
sol-gel layer may be formed upon CFC surface 54, mesa sidewall 55
and recessed surface 57. Additionally, one or more of CFC surface
54, mesa sidewall 55 and recessed surface 57 may be provided with a
roughened surface, for example, providing the same with a fractal
structure, which is subsequently coated with a highly ordered low
surface energy self-assembled monomer layer, as disclosed by
Shibuichi et al. in SUPER WATER-AND OIL-REPELLANT SURFACE RESULTING
FROM FRACTAL STRUCTURE, Journal of Colloid and Interface Science
208, 287-294 (1998). To that end, one or more of CFC surface 54,
mesa sidewall 55 and recessed surface 57 would be subjected to an
anode oxidation method as disclosed therein and then coated with a
composition containing long chain fluorinated silanes, such as, one
of 1H,1H,2H,2H-perfluorooctyltrichlorosilane,
1H,1H,2H,2H-perfluorodecyl phosphate and the like. Monolayers
formed from these structures have been shown to exhibit surface
energies of approximately 6 mN/m.
[0034] With the aforementioned coatings on one or more of CFC
surface 54, mesa sidewall 55 and recessed surface 57, along with
the various shapes with which CFC surface 54 may be configured,
control over the quantity of imprinting material 12 extruding from
the volumetric gap may be greatly facilitated. For example, for a
given quantity of imprinting material 12 and aspect ratio of
recessions 62 it may be possible to arrange the relative surface
energies of CFC surface 54, mesa sidewall 55 and recessed surface
57, as well as the dimensions thereof, whereby a resulting flow
velocity of imprinting material 12 would cause recessions 62 to be
filled with imprinting material 12, before any, or a greater than
desired amount of, imprinting material 12 extrudes outside the
volumetric gap. Thus, the imprinting material 12 may be cured while
minimizing the quantity of uncured imprinting material 12 that
remains and/or the dimension of any extrusions formed.
[0035] In a further embodiment, a further control over the quantity
of imprinting material extruding outside of region 18 is achieved
by exposing the same to an oxygen-rich fluid environment.
Specifically, by directing a stream of oxygen-rich fluid directed
to CFC surface 54, mesa sidewall 55 and recessed surface 57,
imprinting material 12 disposed thereon will be prevented from
curing. Further, exposure to a stream of oxygen may facilitate
evaporation of imprinting material 12 upon which the fluid stream
impinges. Currently, the environs surrounding template 50 are
saturated with helium to prevent trapping of air in imprinting
material 12. However, prior to exposing imprinting layer 12 to
actinic radiation, the stream of oxygen-rich fluid may be
introduced, with or without interrupting the supply of helium.
Furthermore, employing the aforementioned helium flow may
facilitate in varying a shape of an edge of the cured portion of
imprinting material 12 with respect to the CFC surface 54, shown in
FIG. 4, by varying the time of employment of the helium flow with
respect to the imprinting process.
[0036] The embodiments of the present invention described above are
exemplary. Many changes and modifications may be made to the
disclosure recited above, while remaining within the scope of the
invention. Therefore, the scope of the invention should not be
limited by the above description, but instead should be determined
with reference to the appended claims along with their full scope
of equivalents.
* * * * *